The present invention relates to construction between a rotating metal shaft and an inner race of a ceramic bearing to be used in aircraft engines and other industrial rotary machines.
In the fields of aircraft engines and other industrial rotary machines, ceramic bearings have been proposed for use under high temperature and high-velocity severe operating conditions.
FIG. 1 shows one example of conventional ceramic bearings. A ceramic bearing d comprises an inner race b, an outer race c and a plurality of balls a interposed between the races b and c and is mounted to a metal shaft e. Metal taper rings f are interposed between the ceramic inner race b and the metal shaft e so as to absorb difference in thermal expansion between assembling and operation of the ceramic bearing to thereby prevent cracking of the latter.
In the ceramic bearing d of the type described above, difference in thermal expansion between the ceramic inner race b and the metal shaft e is absorbed by axial displacement of the taper rings f, whereby circumferential and radial stresses which may cause cracking of the ceramic inner race b are reduced to moderate values.
However, the ceramic bearing of the type described above has the following problems and defects unsolved:
(a) Due to friction caused by an initial tightening force between the ceramic inner race b and the metal shaft e, the taper rings f may cause sticking and fail to be axially displaced, resulting in low reliability of the ceramic bearings.
(b) Positioning of the paired taper rings f with respect to each other is difficult to carry out.
(c) The taper ring f and tapered portions of the ceramic inner race b must be machined with high accurate dimension so that a number of component parts which requires machining with high accurate dimension is increased, resulting in increase of cost for the ceramic bearings.
The present invention was made to overcome the above and other problems encountered in the conventional ceramic bearings and has for its object to provide a ceramic bearing in which, without increase of component parts, circumferential and radial stresses caused by difference in thermal expansion between the ceramic inner race and the metal shaft can be relieved to thereby prevent cracking of the ceramic inner race.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments thereof taken in conjunction with the accompanying drawings.